This application relates to a method and control for reducing fault energy from an electric motor powering a rotor.
Electric motors are known and utilized to power a number of different articles. One type of electric motor is a permanent magnet motor. In a permanent magnet motor, a motor rotor is provided with permanent magnets.
These motors are becoming widely utilized for high power fan and compressor drive applications. The permanent magnet motors typically offer improved efficiency and can be smaller in size and weight as compared to more standard variable reluctance or induction motors.
There are a number of systems utilized within fan and compressor assemblies. One type system is a variable diffuser, which may adjust position and aperture size based upon signals from a control. The diffuser may be adjusted based upon ambient temperature, altitude (when used in aerospace applications), pressure, flow demand, and other operating conditions. Variable diffusers improve the overall efficiency of the compressor, and the torque demand on the motor.
One application is for a compressor to deliver air into applications on an aircraft, such as air supply for an aircraft cabin. In such a compressor, there is a “add heat supply.” The add heat supply routes air from a compressor outlet through a selectively open valve into a chamber that delivers the air back to the inlet to the compressor. By recirculating some of the air which has been previously heated by the compressor, the temperature of the air delivered to the application, such as an aircraft cabin, is raised.
One challenge with permanent magnet motors occurs during a fault condition.
Should a winding fault, such as a “short circuit,” be detected, a controller will act to shut the motor down. A winding short in many motor types is a fairly benign occurrence. However, in a permanent magnet motor, a gradual spin down of the rotor will cause the motor to act as a generator and feed energy to the fault until the rotational assembly finally comes to rest. This may be undesirable.